Control device for vehicular drive system

Abstract

A vehicular transmission mechanism, switchable between a continuously-variable shifting state and a step-variable shifting state, and a control device for controlling an operation of switching of the shifting state of the transmission mechanism so as to reduce its switching shock and improve the durability of coupling devices. The transmission mechanism 10 is switchable between the electrically established continuously-variable shifting state and the step-variable shifting state, by selective releasing and engaging actions of a switching clutch and brake.

The invention claimed is: 
     
       1. A control device for a vehicular drive system which is arranged to transmit an output of an engine to a drive wheel of a vehicle and which comprises a switchable transmission mechanism including a power distributing mechanism which has a first element fixed to said engine, a second element fixed to a first electric motor, and a third element fixed to a second electric motor and a power transmitting member, and a coupling device operable to connect any two of said first through third elements to each other and/or fix said second element to a stationary member, said switchable transmission mechanism being switchable between a continuously-variable shifting state in which the switchable transmission mechanism is operable as an electrically controlled continuously variable transmission, and a step-variable shifting state in which the switchable transmission mechanism is operable as a step-variable transmission, said control device comprising:
 switching control means for selectively releasing and engaging said coupling device, on the basis of a condition of the vehicle, to place said switchable transmission mechanism selectively in one of said continuously-variable shifting state and said step-variable shifting state; and 
 electric motor control means for controlling said first electric motor so as to generate a reaction torque upon releasing of said coupling device, and/or so as to reduce speed differences among said first element, said second element and said third element or a speed difference between said second element and said stationary member, upon engaging of said coupling device. 
 
     
     
       2. The control device according to  claim 1 , wherein said switching control means is operable to release said coupling device to place said switchable transmission mechanism in said continuously-variable shifting state in which said first, second and third elements are rotatable relative to each other, and operable to engage said coupling device to place the switchable transmission mechanism in said step-variable shifting state in which any two of said first, second and third elements are connected to each other or said second element is held stationary. 
     
     
       3. The control device according to  claim 1 , wherein said switching control means releases said coupling device to switch said switchable transmission mechanism from said step-variable shifting state to said continuously-variable shifting state, said switching control means initiating a releasing action of said coupling device after generation of the reaction torque by said first electric motor under the control of said electric motor control means. 
     
     
       4. The control device according to  claim 1 , wherein said switching control means releases said coupling device to switch said switchable transmission mechanism from said step-variable shifting state to said continuously-variable shifting state, and said electric motor control means controls said first electric motor in the process of a releasing action of said coupling device under the control of said switching control means such that the reaction torque of the first electric motor is increased as the coupling device is released. 
     
     
       5. The control device according to  claim 4 , wherein said electric motor control means feedback-controls a speed of said first electric motor, so as to reduce the speed differences among said first, second and third elements or the speed difference between said second element and said stationary member. 
     
     
       6. The control device according to  claim 3 , wherein said electric control means controls a speed of said first electric motor such that the speed differences among said first, second and third elements or the speed difference between said second element and said stationary member is maintained at a value before initiation of the releasing action of said coupling device, until said releasing action controlled by said switching control means is completed. 
     
     
       7. The control device according to  claim 1 , wherein said switching control means engages said coupling device to switch said switchable transmission mechanism from said continuously-variable shifting state to said step-variable shifting state, said switching control means initiating an engaging action of said coupling device after a speed of said first electric motor has been controlled by said electric motor control means so as to reduce the speed differences among said first, second and third elements or the speed difference between said second element and said stationary member. 
     
     
       8. The control device according to  claim 1 , wherein said switching control means engages said coupling device to switch said switchable transmission mechanism from said continuously-variable shifting state to said step-variable shifting state, said switching control means effecting an engaging action of said coupling device in the process of control of a speed of said first electric motor by said electric motor control means so as to reduce the speed differences among said first, second and third elements or the speed difference between said second element and said stationary member. 
     
     
       9. The control device according to  claim 7 , further comprising engine output control means for controlling a torque or output of said engine, and wherein said engine output control means limits the torque or output of said engine, so as to prevent the torque or output of the engine from exceeding an upper limit determined by a nominal rating of said first electric motor, until the engaging action of said coupling device controlled by said switching control means is completed. 
     
     
       10. The control device according to  claim 1 , wherein said switching control means includes high-speed-running determining means for determining that the vehicle is in a high-speed running state when an actual value of a running speed of the vehicle is higher than a predetermined upper limit value, said switching control means controlling said coupling device to place said switchable transmission mechanism in said step-variable shifting state when said high-speed-running determining means has determined that the vehicle is in said high-speed running state. 
     
     
       11. The control device according to  claim 1 , wherein said switching control means includes high-output-running determining means for determining that the vehicle is in a high-output running state when a drive-force related value of the vehicle is higher than a predetermined upper limit value said switching control means controlling said coupling device to place said switchable transmission mechanism in said step-variable shifting state when said high-output-running determining means has determined that the vehicle is in said high-output running state. 
     
     
       12. The control device according to  claim 1 , wherein said switching control means controls said coupling device to place said switchable transmission mechanism in one of said continuously-variable and step-variable shifting states, on the basis of an actual value of a running speed of the vehicle and an actual value of a drive-force-related value of the vehicle and according to a stored switching boundary line map including a high-speed-running boundary line and a high-output-running boundary line which are defined by parameters in the form of said running speed of the vehicle and said drive-force-related value. 
     
     
       13. The control device according to  claim 1 , wherein said switching control means includes electric-path-function diagnosing means for determining whether a function of any one of control components for placing said switchable transmission mechanism said continuously-variable shifting state is deteriorated, said switching control means controlling said coupling device to place said switchable transmission mechanism in said step-variable shifting state when said electric-path-function diagnosing means has determined that the function of said any one of the control components is deteriorated. 
     
     
       14. The control device according to  claim 1 , wherein said power distributing mechanism is a planetary gear set, including a carrier functioning as said first element, a sun gear functioning as said second element and a ring gear functioning as said third element,
 and wherein said coupling device includes a clutch operable to connect any two of said carrier, sun gear and ring gear to each other, and/or a brake operable to fix said sun gear to said stationary member. 
 
     
     
       15. The control device according to  claim 14 , wherein said planetary gear set is a single-pinion. 
     
     
       16. The control device according to  claim 1 , wherein said power distributing mechanism is a differential gear device, and said coupling device includes a clutch operable to connect any two of said first, second and third elements, and/or a brake operable to fix said second element to said stationary member. 
     
     
       17. The control device according to  claim 16 , wherein said differential gear device is a bevel-gear. 
     
     
       18. The control device according to  claim 14 , wherein said switching control means engages said clutch to enable said power distributing mechanism to operate as a transmission having a speed ratio of 1, or engages said brake to enable said power distributing mechanism to operate as a speed-increasing transmission having a speed ratio lower than 1. 
     
     
       19. The control device according to  claim 1 , wherein said switchable transmission mechanism includes an automatic transmission disposed between said power transmitting member and said drive wheel and connected in series to said power distributing mechanism, and has a speed ratio determined by a speed ratio of said automatic transmission. 
     
     
       20. The control device according to  claim 19 , wherein said switchable transmission mechanism has an overall speed ratio defined by a speed ratio of the power distributing mechanism and the speed ratio of said automatic transmission. 
     
     
       21. The control device according to  claim 19 , wherein said automatic transmission is a step-variable automatic transmission which is shifted according to a stored shifting boundary line map. 
     
     
       22. A control device for a vehicular drive system including a differential portion which is operable as an electrically controlled differential device and which includes a differential mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member and having a plurality of rotary elements, and a second electric motor disposed in a power transmitting path between said power transmitting member and a drive wheel of a vehicle,
 said differential mechanism including a coupling device operable to switch said differential portion between a differential state in 
 
       which said differential portion is operable as the electrically controlled differential device and is capable of performing a differential function, and a locked state in which said differential portion is not capable of performing said differential function, said control device comprising:
 switching control means for selectively releasing and engaging said coupling device, on the basis of a condition of the vehicle, to place said differential portion selectively in one of said differential state and said locked state; and 
 electric motor control means for controlling said first electric motor so as to generate a reaction torque upon releasing of said coupling device, and/or so as to reduce speed differences among said plurality of rotary elements or a speed difference between one of said plurality of rotary elements to which said first electric motor is fixed, and a stationary member, upon engaging of said coupling device. 
 
     
     
       23. The control device according to  claim 22 , wherein said plurality of rotary elements of said differential mechanism consist of a first element fixed to said engine, a second element fixed to said first electric motor, and a third element fixed to said power transmitting member, and said coupling device is operable to connect any two of said first through third elements, and/or fix said second element to said stationary member. 
     
     
       24. The control device according to  claim 23 , wherein said switching control means is operable to release said coupling device to place said differential portion in said differential state in which said first, second and third elements are rotatable relative to each other, and operable to engage said coupling device to place said differential portion in said locked state in which said first, second and third elements are rotated as a unit or said second element is held stationary. 
     
     
       25. The control device according to  claim 23 , wherein said switching control means releases said coupling device to switch said differential portion from said locked state to said differential state, said switching control means initiating a releasing action of said coupling device after generation of the reaction torque by said first electric motor under the control of said electric motor control means. 
     
     
       26. The control device according to  claim 23 , wherein said switching control means releases said coupling device to switch said differential portion from said locked state to said differential state, and said electric motor control means controls said first electric motor in the process of a releasing action of said coupling device under the control of said switching control means such that the reaction torque of the first electric motor is increased as the coupling device is released. 
     
     
       27. The control device according to  claim 26 , wherein said electric motor control means feedback-controls a speed of said first electric motor, so as to reduce the speed differences among said first, second and third elements or the speed difference between said second element and said stationary member. 
     
     
       28. The control device according to  claim 25 , wherein said switching control means controls a speed of said first electric motor such that the speed difference among said first, second and third elements or the speed difference between said second element and said stationary member is maintained at a value before initiation of the releasing action of said coupling device, until said releasing action controlled by said switching control means is completed. 
     
     
       29. The control device according to  claim 23 , wherein said switching control means engages said coupling device to switch said differential portion from said differential state to said locked state, said switching control means initiating an engaging action of said coupling device after a speed of said first electric motor has been controlled by said electric motor control means so as to reduce the speed differences among said first, second and third elements or the speed difference between said second element and said stationary member. 
     
     
       30. The control device according to  claim 23 , wherein said switching control means engages said coupling device to switch said differential portion from said differential state to said locked state, said switching control means effecting an engaging action of said coupling device in the process of control of a speed of said first electric motor by said electric motor control means so as to reduce the speed differences among said first, second and third elements or the speed difference between said second element and said stationary member. 
     
     
       31. The control device according to  claim 29 , further comprising engine output control means for controlling a torque or output of said engine, and wherein said engine output control means limits the torque or output of the engine, so as to prevent the torque or output of the engine from exceeding an upper limit determined by a nominal rating of said first electric motor, until the engaging action of said coupling device controlled by said switching control means is completed. 
     
     
       32. The control device according to  claim 23 , wherein said switching control means includes high-speed-running determining means for determining that the vehicle is in a high-speed running state when an actual value of a running speed of the vehicle is higher than a predetermined upper limit value, said switching control means controlling said coupling device to place said differential portion in said locked state when said high-speed-running determining means has determined that the vehicle is in said high-speed running state. 
     
     
       33. The control device according to  claim 23 , wherein said switching control means includes high-output-running determining means for determining that the vehicle is in a high-output running state when a drive-force-related value of the vehicle is higher than a predetermined upper limit value, said switching control means controlling said coupling device to place said differential portion in said locked state when said high-output-running determining means has determined that the vehicle is in said high-output running state. 
     
     
       34. The control device according to  claim 23 , wherein said switching control means controls said coupling device to place said differential portion in one of said differential state and locked states, on the basis of an actual value of a running speed of the vehicle and an actual value of a drive-force-related value of the vehicle and according to a stored switching boundary line map including a high-speed-running boundary line and a high-output-running boundary line which are defined by parameters in the form of said running speed of the vehicle and said drive-force-related value. 
     
     
       35. The control device according to  claim 23 , wherein said switching control means includes electric-path-function diagnosing means for determining whether a function of any one of control components for enabling said differential portion to operate as said electrically controlled differential device is deteriorated, said switching control means controlling said coupling device to place said differential portion in said locked state when said electric-path-function diagnosing means has determined that the function of said any one of the control components is deteriorated. 
     
     
       36. The control device according to  claim 23 , wherein said differential mechanism is a planetary gear set, including a carrier functioning as said first element, a sun gear functioning as said second element and a ring gear functioning as said third element,
 and wherein said coupling device includes a clutch operable to connect any two of said carrier, sun gear and ring gear to each other, and/or a brake operable to fix said sun gear to said stationary member. 
 
     
     
       37. The control device according to  claim 36 , wherein said planetary gear set is a single-pinion. 
     
     
       38. The control device according to  claim 23 , wherein said differential mechanism is a differential gear device, and said coupling device includes a clutch operable to connect any two of said first, second and third elements, and/or a brake operable to fix said second element to said stationary member. 
     
     
       39. The control device according to  claim 38 , wherein said differential gear device is a bevel-gear. 
     
     
       40. The control device according to  claim 36 , wherein said switching control means engages said clutch to enable said differential mechanism to operate as a transmission having a speed ratio of 1, or engages said brake to enable said differential mechanism to operate as a speed-increasing transmission having a speed ratio lower than 1. 
     
     
       41. The control device according to  claim 23 , wherein said power transmitting path includes an automatic transmission portion, and said vehicular drive system has an overall speed ratio defined by a speed ratio of said automatic transmission portion and a speed ratio of said differential portion. 
     
     
       42. The control device according to  claim 41 , wherein said automatic transmission portion is a step-variable automatic transmission which is shifted according to a stored shifting boundary line map. 
     
     
       43. The control device according to  claim 4 , wherein said electric control means controls a speed of said first electric motor such that the speed differences among said first, second and third elements or the speed difference between said second element and third elements or the speed difference between said second element and said stationary member is maintained at a value before initiation of the releasing action of said coupling device, until said releasing action controlled by said switching control means is completed. 
     
     
       44. The control device according to  claim 8 , further comprising engine output control means for controlling a torque or output of said engine, and wherein said engine output control means limits the torque or output of said engine, so as to prevent the torque or output of the engine from exceeding an upper limit determined by a nominal rating of said first electric motor, until the engaging action of said coupling device controlled by said switching control means is completed. 
     
     
       45. The control device according to  claim 16 , wherein said switching control means engages said clutch to enable said power distributing mechanism to operate as a transmission having a speed ratio of 1, or engages said brake to enable said power distributing mechanism to operate as a speed-increasing transmission having a speed ratio lower than 1. 
     
     
       46. The control device according to  claim 26 , wherein said switching control means controls a speed of said first electric motor such that the speed difference among said first, second and third elements or the speed difference between said second element and said stationary member is maintained at a value before initiation of the releasing action of said coupling device, until said releasing action controlled by said switching control means is completed. 
     
     
       47. The control device according to  claim 30 , further comprising engine output control means for controlling a torque or output of said engine, and wherein said engine output control means limits the torque or output of the engine, so as to prevent the torque or output of the engine from exceeding an upper limit determined by a nominal rating of said first electric motor, until the engaging action of said coupling device controlled by said switching control means is completed. 
     
     
       48. The control device according to  claim 38 , wherein said switching control means engages said clutch to enable said differential mechanism to operate as a transmission having a speed ratio of 1, or engages said brake to enable said differential mechanism to operate as a speed-increasing transmission having a speed ratio lower than 1. 
     
     
       49. A control device for a vehicular drive system including a differential portion which is operable as an electrically controlled differential device and which includes a differential mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member and having a plurality of rotary elements, and a second electric motor connected with the power transmitting member in a power transmittable manner, the differential mechanism including a coupling device operable to switch the differential portion between a differential state in which the differential portion is operable as the electrically controlled differential device and is capable of performing a differential function, and a locked state in which the differential portion is not capable of performing the differential function, the control device comprising:
 switching control means for selectively releasing and engaging the coupling device, on the basis of a condition of the vehicle, to place the differential portion selectively in one of the differential state and the locked state; and 
 electric motor control means for controlling the first electric motor so as to generate a reaction torque upon releasing of the coupling device, and/or so as to reduce speed differences among the plurality of rotary elements or a speed difference between one of the plurality of rotary elements to which the first electric motor is fixed, and a stationary member, upon engaging of the coupling device.